How does Finland deal in practice with instances of alleged violations of the demilitarised and neutralised zone of the Åland Islands? This is the main question in this text. We examine three levels of regulation and practice, namely international law, legislation concerning territorial surveillance and criminal law during the period 2010–2015. We examine unique materials obtained upon application. We conclude that the criminalisation presents Finland with several advantages but also some problems, in particular in matters of criminal liability. The absence of easily accessible and visible nautical and aeronautical charts indicating the coordinates of the demilitarised and neutralised zone for all those practically concerned remains a major obstacle. While the total number of reported violations remains low, the investigations confirm the continued validity of the demilitarisation regime and the intricate interplay between domestic and international law.